A solar cell is expected as a new energy source because the solar cell directly converts clean and inexhaustibly supplied sunlight into electricity.
In general, energy output per solar cell is approximately several watts. Accordingly, when solar cells are used as a power source for a house, a building or the like, a solar cell module is used in which a plurality of solar cells are connected to each other to enhance energy output.
The plurality of solar cells are electrically connected to each other through a wiring member and sealed with a sealant. The wiring member is connected onto a connection electrode formed on the main surface of each solar cell.
Here, a method is proposed in which a resin adhesive is inserted between the wiring member and the connection electrode to bond the wiring member to the connection electrode, the resin adhesive being thermally cured at a temperature lower than the melting temperature of a solder (see JP-A 2007-214533, for example). An electrical connection between the wiring member and the connection electrode is established through a plurality of conductive particles included in the resin adhesive. With the method, the influence of temperature change on a solar cell can be reduced as compared to the case where the wiring member is soldered to the connection electrode.
However, most of the conductive particles are located dispersed from each other. Hence, there is a problem in which it is difficult to maintain a favorable electrical connection between the connection electrode and the wiring member due to the displacement of the conductive particles existing between the connection electrode and the wiring member.
To be more specific, since the sealant has a linear expansion coefficient larger than that of the wiring member, the wiring member receives stress from the sealant due to temperature change under environment where the solar cell module is used. Such stress is transmitted to the resin adhesive and thereby deforms the resin adhesive. This displaces the positions of the conductive particles in the resin adhesive, and consequently causes a problem in which an electrical connection cannot be established in some portions.
Such a problem is likely to occur when projections are formed on a wiring-member-side surface of the connection electrode and when the conductive particles sandwiched between the projections and the wiring member are moved from between the projections and the wiring member.
The present invention has been made in view of the above problem. An object thereof is to provide a solar cell module capable of maintaining a favorable electrical connection between a wiring member and a connection electrode.